Related rates and implicit

A spherical balloon is being filled with helium at a rate of 8cm^3/s at what rate is the radius increasing when the radius is 12cm, when the volume is 1435cm^3 and when it has bee filling for 33.5 sec

the angle between two intersecting curves is defined as the angle between their tangents at the point of intersection. If this angel is 90 degrees, the two curves are said to be orthogonal. prove that the curves defined by x^2-y^2=k and xy=p intersect orthogonally for all values of the constants k and p. Illustrate your proof with a sketch .